CN109150780B - WiFi ToF ranging positioning system based on channel state information - Google Patents

WiFi ToF ranging positioning system based on channel state information Download PDF

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CN109150780B
CN109150780B CN201810921247.5A CN201810921247A CN109150780B CN 109150780 B CN109150780 B CN 109150780B CN 201810921247 A CN201810921247 A CN 201810921247A CN 109150780 B CN109150780 B CN 109150780B
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CN109150780A (en
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邵力斌
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Nanjing Rongfei Technology Co ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0014—Carrier regulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2689—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation
    • H04L27/2695—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation with channel estimation, e.g. determination of delay spread, derivative or peak tracking
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
    • H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
    • H04L27/38—Demodulator circuits; Receiver circuits
    • H04L27/3845—Demodulator circuits; Receiver circuits using non - coherent demodulation, i.e. not using a phase synchronous carrier
    • H04L27/3854—Demodulator circuits; Receiver circuits using non - coherent demodulation, i.e. not using a phase synchronous carrier using a non - coherent carrier, including systems with baseband correction for phase or frequency offset
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/0001—Arrangements for dividing the transmission path
    • H04L5/0003—Two-dimensional division
    • H04L5/0005—Time-frequency
    • H04L5/0007—Time-frequency the frequencies being orthogonal, e.g. OFDM(A), DMT
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0053—Allocation of signaling, i.e. of overhead other than pilot signals
    • H04L5/0057—Physical resource allocation for CQI
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/30—Services specially adapted for particular environments, situations or purposes
    • H04W4/33—Services specially adapted for particular environments, situations or purposes for indoor environments, e.g. buildings
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/80—Services using short range communication, e.g. near-field communication [NFC], radio-frequency identification [RFID] or low energy communication
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W64/00—Locating users or terminals or network equipment for network management purposes, e.g. mobility management
    • H04W64/006—Locating users or terminals or network equipment for network management purposes, e.g. mobility management with additional information processing, e.g. for direction or speed determination
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0014—Carrier regulation
    • H04L2027/0024—Carrier regulation at the receiver end
    • H04L2027/0026—Correction of carrier offset

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Abstract

The invention discloses a WiFi (wireless fidelity) ToF (ToF) ranging and positioning system based on channel state information, which comprises a base station and a mobile point terminal, wherein the base station comprises a WiFi module, the WiFi module is connected with a CSI (channel state information) extraction module, the CSI extraction module is connected with an equipment transmission phase error elimination module, the equipment transmission phase error elimination module is connected with a phase extraction and subcarrier phase error elimination module, the phase extraction and subcarrier phase error elimination module is connected with a ToF ranging module, and the equipment transmission phase error elimination module and the WiFi module perform bidirectional signal transmission. The equipment transmission phase error elimination module is used for eliminating phase transceiving errors existing between two communication equipment. The invention adds an equipment transmission phase error elimination module for eliminating the phase offset caused by transmission between equipment, thereby ensuring the reliability of phase ranging and improving the measurement precision.

Description

WiFi ToF ranging positioning system based on channel state information
Technical Field
The invention relates to the technical field of wireless positioning, in particular to a WiFi (wireless fidelity) ToF (ToF) ranging and positioning system based on channel state information.
Background
From star map navigation to compass, from GPS to indoor positioning, people's demand for location services has been ancient to date. Among the positioning technologies in the present society, the wireless positioning technology has become the mainstream positioning technology due to its characteristics of high penetrability, wide coverage, over-the-horizon transmission, low price, and the like. With the development of the internet of things industry, people have higher and higher requirements on positions, and the traditional wireless positioning precision (2M-10M) cannot meet the current requirements gradually. For example, in the field of positioning and tracking of unmanned aerial vehicles, or indoor electronic fences, etc., there are high demands on positioning accuracy.
Thus, a range of high precision wireless location technologies, such as UWB, have emerged. However, the UWB technology requires additional deployment of UWB base stations, which is not only expensive, but also causes problems such as redundancy or low utilization of devices in space, because the devices are only positioning devices for ordinary users. The best solution to this problem is to use the WiFi devices that are currently in the vicinity for wireless location.
Due to the popularity of WiFi, research and application of WiFi positioning has become a hotspot in recent years.
A lot of WiFi positioning technologies are emerging in academia and market, and most of these technologies are based on RSSI field strength signal or RSSI fingerprint information for positioning. Since WiFi is not a special positioning device, its frequency band is also strongly interfered by the environment, and the general positioning accuracy is only 5M-10M by using the above positioning technology.
In order to solve the problem of low accuracy of the conventional WiFi positioning technology, in recent two years, the academia has focused on CSI channel status information provided in the 802.11n protocol, and many IEEE802.11 standards use OFDM modulation signals, which are transmitted through a plurality of orthogonal subcarriers, where the signals transmitted on each subcarrier have different signal strengths and phases.
Specifically, one sample of CFR within the WiFi bandwidth range may be output in the form of CSI:
H＝[H(f1)，H(f2)，…，H(fi)，…，H(fN)]T，i∈[1，30]。
each CSI characterizes the amplitude and phase of one subcarrier.
The CN 106950538A patent of the university of harbin industry discloses a ToF ranging method based on the chinese remainder theorem. The method comprises the following steps of:
1. obtaining CSI information of multiple frequencies by frequency hopping
2. Extracting phase information from CSI
3. Cancelling phase in channel state information
4. ToF solution by using Chinese remainder theorem
Theoretically, this method is feasible, and the ToF time can be solved by using frequency hopping, however, in step 3, there is still a problem in eliminating the phase in the channel state information.
In step 3, the sub-carrier No. 0 of the OFDM is used to remove the phase offset caused by the frequency difference between the sub-carriers, but besides this offset, there still exist many errors in the interaction process between the transmitting end and the receiving end, such as PLL phase-locked loop offset of different frequencies and frequency offset of antenna processing. Even if the phase detection is not accurate due to the absence of a high-precision clock. Various factors result in the method not being able to remove the phase error, so that the final ToF ranging cannot be performed using the architecture.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a high-precision WiFi ToF ranging and positioning system based on channel state information.
The purpose of the invention is realized by the following technical scheme.
A WiFi ToF ranging and positioning system based on channel state information comprises a base station and a mobile point terminal, the base station comprises a WiFi module, the WiFi module is connected with a CSI extraction module, the WiFi module is in one-way signal transmission with the CSI extraction module, the CSI extraction module is connected with an equipment transmission phase error elimination module, the CSI extraction module is in one-way signal transmission to an equipment transmission phase error elimination module which is connected with a phase extraction and subcarrier phase error elimination module, the device transmits a one-way signal transfer from the phase error cancellation module to the phase extraction and subcarrier phase error cancellation module, the phase extraction and subcarrier phase error elimination module is connected with a ToF ranging module, the phase extraction and subcarrier phase error elimination module transmits signals to the ToF ranging module in a one-way mode, and the equipment transmission phase error elimination module transmits signals in a two-way mode to the WiFi module.
Further, the device transmission phase error elimination module is used for eliminating phase transceiving errors existing between two communication devices.
Further, the phase transceiving error includes a processing error at the transmitting end, an antenna transmission error, and a processing error at the receiving end.
Further, the mobile point end comprises a WiFi positioning module, the WiFi positioning module and the WiFi module are in bidirectional signal transmission through an antenna array, and the WiFi positioning module is connected with a high-precision clock.
Further, the method for eliminating the phase transceiving error existing between the two communication devices comprises the following steps:
a positioning frame transmitted by a positioning base station is modulated by MIMO and OFDM methods and then transmitted by an antenna array, and at the moment, a phase-locked loop at a transmitting end generates phase offset
Figure BDA0001763286100000021
The modulated A positioning frame is transmitted in the space, and tiny frequency deviation f is generated in the transmitting process of the base station antenna arrayAThe micro frequency offset f is generated in the receiving process of the antenna array at the mobile point endBThe phase shift generated in this process is related to the signal flight time τ;
the modulated A positioning frame is captured by a mobile point terminal B and processed by a mobile point terminal chip to obtain CSIABAt this time, the frequency deviation of the sending end phase-locked loop is generated
Figure BDA0001763286100000031
The phase value analyzed at this time includes the following errors
Figure BDA0001763286100000032
Using a CSI channel model representation, then
Figure BDA0001763286100000033
Wherein the CSIrxIndicating the received channel CSI data, H indicating the non-shifted CSI data,
Figure BDA0001763286100000034
is that
Figure BDA0001763286100000035
The resulting offset;
the high-precision clock ensures that the chip sends a frame back when receiving the signal;
the WiFi positioning module at the mobile point end modulates a return frame by the MIMO and OFDM methods, and transmits the return frame through the antenna array, and at the moment, the phase shift is generated due to the phase-locked loop at the mobile point end
Figure BDA0001763286100000036
The modulated return frame is transmitted in the space, and tiny frequency deviation f is generated in the process of transmitting the mobile point terminal antennaBThe base station antenna generates a tiny frequency deviation f in the receiving processA；
The modulated return frame is captured by the base station A and processed by the base station chip to obtain CSIBAPLL frequency offset generated at this time
Figure BDA0001763286100000037
In the above transmission process, the mobile station will receive the CSIABTransmitting the CSI received by the mobile point end to a base stationABThe transmission mode to the base station comprises: transmitting the CSI on a return frameABAs data, sent together; or separately transmitting the CSI after the return frame is transmittedABAs data to the base station; or the mobile point terminal sends the CSIABSending the data to a server as data, and sending the data to a base station by the server;
using a CSI channel model representation, then
Figure BDA0001763286100000038
CFO elimination algorithm, the principle is to pass through CSIABAnd CSIBAThe calculation of (2) eliminates the error generated in the middle;
according to the CSI channel model, there is CSIABCSIBA＝H2The CFO phase offset can be eliminated.
Further, the phase extraction and subcarrier phase error elimination module is configured to estimate a phase of a subcarrier 0 in the OFDM propagation model to obtain a final phase value.
Further, the CSI extracting module is configured to extract a CSI matrix from the WiFi module.
Further, the ToF ranging module is configured to perform ToF distance estimation according to the phase value.
Furthermore, the ToF distance estimation can obtain ToF values of different frequencies by using a frequency hopping sampling technology, and then the ToF distance estimation is solved by using the Chinese remainder theorem to obtain the unique ToF value.
Further, the estimating the phase of the sub-carrier 0 in the OFDM propagation model to obtain a final phase value specifically includes:
the base station WiFi model processes the CSI signals after CFO elimination, 30 subcarrier phase values of OFDM are extracted, and in the wireless signal propagation model of OFDM, the phase value of each subcarrier
Figure BDA0001763286100000041
In the presence of frequency deviation fi，
Figure BDA0001763286100000042
For the carrier transmit frequency, τ is the time of flight, which is related as follows:
Figure BDA0001763286100000043
since the sub-carrier No. 0 has no frequency offset and the OFDM sub-carriers are numbered-15, -14. -1, 1.., 14,15, the phase values of the sub-carrier No. 0 are estimated using the phase values of-1 and 1.
Compared with the prior art, the invention has the advantages that: the invention adds an equipment transmission phase error elimination module for eliminating the phase offset caused by transmission between equipment, thereby ensuring the reliability of phase ranging and improving the measurement precision.
Drawings
Fig. 1 is a diagram illustrating a base station structure according to the present invention.
Fig. 2 is a schematic diagram of the system of the present invention.
Fig. 3 is a flow chart of the apparatus transmission phase error cancellation data of the present invention.
Detailed Description
The invention is described in detail below with reference to the drawings and specific examples.
As shown in fig. 1, a WiFi ToF ranging and positioning system based on channel state information includes a base station and a mobile point terminal, the base station includes a WiFi module, the WiFi module is connected with a CSI extraction module, the WiFi module transmits a signal to the CSI extraction module in a unidirectional manner, the CSI extraction module is connected with a device transmission phase error cancellation module, the CSI extraction module transmits a signal to the device transmission phase error cancellation module in a unidirectional manner, the device transmission phase error cancellation module is connected with a phase extraction and subcarrier phase error cancellation module, the device transmission phase error cancellation module transmits a signal to the phase extraction and subcarrier phase error cancellation module in a unidirectional manner, the phase extraction and subcarrier phase error cancellation module is connected with a ToF ranging module, the phase extraction and subcarrier phase error cancellation module transmits a signal to the ToF ranging module in a unidirectional manner, the equipment transmission phase error elimination module and the WiFi module carry out bidirectional signal transmission.
And the CSI extraction module is used for extracting a CSI matrix from the WiFi chip and providing the CSI matrix as input to the phase extraction module.
The equipment transmission phase error elimination module has the function of eliminating phase transceiving errors existing between two communication equipment, wherein the errors comprise a transmitting end processing error, an antenna transmission error and a receiving end processing error. A bi-directional phase offset cancellation algorithm, which is illustrated in fig. 3, is used to perform an error cancellation operation on the carrier, so that the extracted CSI matrix is relatively accurate.
The function of the phase extraction and subcarrier phase error cancellation block is to extract the exact phase value from the CSI. Since the CSI stores information of several subcarriers of OFDM, it is possible to directly extract phase values of the subcarriers of each frame. In actual propagation, because there is a frequency difference between subcarriers, the module needs to provide a method to eliminate phase measurement error, and in the OFDM propagation model, the phase value of subcarrier No. 0 has no offset, so the phase of subcarrier No. 0 is estimated to obtain the final phase value.
The ToF ranging module has the function of estimating the ToF distance according to the phase value, the existing technology, such as the frequency hopping sampling technology, can be used for obtaining the ToF values of different frequencies, the values and the solved phase value present a periodic relation under specific frequencies, and then the Chinese remainder theorem is used for solving to obtain the unique ToF value.
As shown in fig. 2, in one positioning process, the left device serves as a base station, and the right device serves as a mobile station.
Step 1: the base station chip assigns a frequency and sends a request through a frequency hopping protocol.
And the mobile point receives the request and performs frequency hopping.
Step 2: after receiving the request, the mobile point end immediately feeds back the high-precision clock to the chip, and the chip sends the received CSI1 serving as data to the base station.
And the base station receives the CSI2 sent by the mobile point terminal and the analyzed CSI 1. As an input of the two-way confirmation mechanism, the phase offset cancellation between the devices is performed, and the details of the algorithm implementation are shown in the algorithm description of fig. 3.
And step 3: the base station chip processes the CSI signals after CFO elimination, extracts the phase values of 30 subcarriers of OFDM, and in a wireless signal propagation model of OFDM, the phase value of each subcarrier
Figure BDA0001763286100000051
In the presence of frequency deviation fi，(
Figure BDA0001763286100000052
For carrier transmit frequency, τ is time of flight), the relationship is as follows:
Figure BDA0001763286100000061
since the sub-carrier No. 0 has no frequency offset and the OFDM sub-carriers are numbered-15, -14. -1, 1.., 14,15, the phase values of the sub-carrier No. 0 are estimated using the phase values of-1 and 1.
And 4, step 4: phase value phi and frequency according to a wireless signal propagation model
Figure BDA0001763286100000062
The time of flight τ is related as follows:
Figure BDA0001763286100000063
therefore, the obtained phase values of a plurality of frequencies are used as the input of the Chinese remainder theorem to obtain the solution of the flight time tau.
And 5: if the unique solution can be obtained in step 4, ToF is output, and the positioning system is finished.
Otherwise, continuing to collect phase values of other frequencies, and repeating the process.
A CSI extraction module: the CSI information provided in the 802.11n protocol includes all information of the wireless channel, and the CSI matrix of each frame can be extracted from the WiFi module through CSI Tools. The protocol utilizes OFDM technology + MIMO technology to transmit, and amplitude, phase, RSSI information and the like of 30 subcarriers can be obtained by analyzing CSI.
However, the CSI information provided by 802.11n includes subcarrier frequency offset and phase offset caused by inter-device transmission in the actual transmission process, and therefore, after the CSI information is extracted, the phase offset in the CSI information needs to be eliminated.
The device transmission phase error elimination module, as mentioned above, can utilize the method of high precision clock + two-way confirmation mechanism to eliminate the phase offset between devices caused by the propagation between devices. The algorithm process is as shown in fig. 3, the module is at the mobile node, and needs to send the received CSI information to the WiFi module of the base station; the module acquires the CSI information from the step 2 at the base station, and directly acquires the CSI information received by the mobile point terminal from the WiFi module, and bidirectional error elimination is carried out through the operation of the two CSI. This is a two-way confirmation mechanism that requires direct interaction with the WiFi module.
The phase extraction and subcarrier phase error elimination module obtains CSI data only with SFO after elimination of equipment transmission phase error, the CSI can extract phase values of 30 subcarriers, and the number 0 subcarrier does not have SFO according to an OFDM channel transmission model, so that elimination can be performed.
For the phase value p after the offset is eliminated, the periodic relation between the flight time t and the carrier frequency f can be calculated through a formula.
The ToF ranging module collects phase values at different frequencies, with different periodic time of flight for different frequencies according to step 5. And solving the flight time by adopting the Chinese remainder theorem.
As shown in fig. 3, a method for removing phase error of inter-device CSI measurement based on bidirectional interaction.
For resolving phase offsets caused by device random variations over time in the propagation of wireless signals.
Step 1: the device transmission phase elimination module starts phase offset elimination and initiates a request to the WiFi module.
Step 2: and (3) after receiving the request in the step (1), the WiFi module of the positioning base station A sends a positioning frame, and the positioning frame is modulated by an MIMO and OFDM method and then sent through an antenna array. At this time, a phase shift is generated due to a Phase Locked Loop (PLL) of a transmitting end
Figure BDA0001763286100000071
And step 3: the modulated A positioning frame is transmitted in space, and tiny frequency deviation f is generated in the process of transmitting the base station antennaAThe small frequency deviation f is generated in the receiving process of the mobile point terminal antennaBThe phase shift generated in the process is related to the time of flight tau of the signal
And 4, step 4: the modulated A positioning frame is captured by a mobile point terminal B and processed by a mobile point terminal chip to obtain CSIABAt this time, PLL frequency offset is generated
Figure BDA0001763286100000072
The phase value analyzed at this time includes the following errors
Figure BDA0001763286100000073
Using a CSI channel model representation, then
Figure BDA0001763286100000074
Wherein the CSIrxIndicating the received channel CSI data, H indicating the non-shifted CSI data,
Figure BDA0001763286100000075
is that
Figure BDA0001763286100000076
The resulting offset.
And 5: the high-precision clock ensures that the chip sends a frame back when receiving the signal and simultaneously sends the received signal CSIABAnd the CSI is transmitted to a CSI extraction module of the mobile point terminal B by the WiFi module.
Step 6: the mobile point end chip modulates the return frame through the MIMO and OFDM sides and sends the return frame through the antenna array. When the phase shift is generated due to the Phase Locked Loop (PLL) at the moving point end
Figure BDA0001763286100000077
And 7: the modulated return frame is transmitted in the space, and tiny frequency deviation f is generated in the process of transmitting the mobile point terminal antennaBThe base station antenna generates a tiny frequency deviation f in the receiving processA
And 8: the modulated return signal is captured by the WiFi module of the base station A, the WiFi module sends the data to the CSI extraction module for analysis, and the WiFi module of the base station A generates PLL frequency offset after processing
Figure BDA0001763286100000081
And step 9: the CSI extraction module analyzes the channel state information CSI of the response frame from the mobile node B to the base station ABAUsing a CSI channel model representation, then
Figure BDA0001763286100000082
Step 10: the CSI extraction module of the base station A extracts the CSIBAAnd transmitting the data to a device transmission phase elimination module.
In particular, in the above flow, step 5 is to transmit the signal transmitted from the base station a to the mobile station B to the CSI extraction module of the mobile station B. The subsequent process is independent from the above process. CSI extracted by CSI extraction module of mobile point terminal BABData transmissionThe process is as follows:
step a: the CSI extraction module of the mobile point terminal B extracts the CSIABAnd transmitting to the device a phase cancellation module.
Step b: the equipment transmit phase cancellation module needs to receive the CSI from the mobile station according to a specific strategy (as described in the claims, during the above transmission process, the mobile station needs to receive the CSIABThe transmission to the base station may be in the following ways: 1. transmitting the CSI on a return frameABAs data, sent together; 2. transmitting the CSI alone after the return frameABAs data to the base station; 3. mobile point terminal sends CSIABAs data to the server, and to the base station via the server. ) To measure CSIABAs data, the data is transmitted to the positioning server via the WiFi module in fig. 3, or directly to the base station a.
Step c: device transmit phase cancellation module takes CSI from WiFi module of base station AABAnd (4) data.
Step 10&After all the steps c are finished, the equipment transmission phase elimination module carries out phase elimination by adopting the principle of CSIABAnd CSIBAThe calculation of (c) eliminates the error that is generated in the middle.
According to the CSI channel model, there is CSIABCSIBA＝H2. The CFO phase offset can be eliminated.
It is particularly noted that in step 5, since the PLL and CFO vary randomly with time, depending on the accuracy of the high-precision clock, the delay in transmission is also taken into account, and therefore, there is still a small amount of offset error.

Claims (5)

1. A WiFi ToF ranging positioning system based on channel state information comprises a base station and a mobile point terminal, wherein the base station comprises a WiFi module, and is characterized in that the WiFi module is connected with a CSI extraction module, the WiFi module is in one-way signal transmission with the CSI extraction module, the CSI extraction module is connected with an equipment transmission phase error elimination module, the CSI extraction module is in one-way signal transmission with the equipment transmission phase error elimination module, the equipment transmission phase error elimination module is connected with a phase extraction and subcarrier phase error elimination module, the equipment transmission phase error elimination module is in one-way signal transmission with the phase extraction and subcarrier phase error elimination module, the phase extraction and subcarrier phase error elimination module is connected with a ToF ranging module, and the phase extraction and subcarrier phase error elimination module is in one-way signal transmission with the ToF ranging module, the device transmission phase error elimination module is in bidirectional signal transmission with the WiFi module, the device transmission phase error elimination module is used for eliminating phase transceiving errors between two communication devices, the phase transceiving errors comprise transmitting end processing errors, antenna transmission errors and receiving end processing errors, the moving point end comprises the WiFi positioning module, the WiFi positioning module and the WiFi module are in bidirectional signal transmission through an antenna array, the WiFi positioning module is connected with a high-precision clock, the CSI extraction module is used for extracting a CSI matrix from the WiFi module, and the ToF ranging module is used for estimating the ToF distance according to a phase value.
2. The system of claim 1, wherein the method for eliminating phase transceiving error between two communication devices comprises:
a positioning frame transmitted by a positioning base station is modulated by MIMO and OFDM methods and then transmitted by an antenna array, and at the moment, a phase-locked loop at a transmitting end generates phase offset
Figure DEST_PATH_IMAGE001
；
The modulated A positioning frame is transmitted in space, and tiny frequency deviation is generated in the transmitting process of the base station antenna array
Figure DEST_PATH_IMAGE002
The micro frequency offset is generated in the receiving process of the mobile point end antenna array
Figure DEST_PATH_IMAGE003
Phase offset and signal time of flight generated during this process
Figure DEST_PATH_IMAGE004
(ii) related;
the modulated A positioning frame is captured by a mobile point end B and is processed by a mobile point end chip to obtain the A positioning frame
Figure DEST_PATH_IMAGE005
At this time, the frequency deviation of the sending end phase-locked loop is generated
Figure DEST_PATH_IMAGE006
The phase value analyzed at this time includes the following error (
Figure DEST_PATH_IMAGE007
）；
Figure DEST_PATH_IMAGE008
For the phase offset generated during the transmission of the base station antenna array,
Figure DEST_PATH_IMAGE009
the phase offset generated in the receiving process of the antenna array at the mobile point end is obtained;
using a CSI channel model representation, then
Figure DEST_PATH_IMAGE010
Wherein
Figure 333996DEST_PATH_IMAGE005
Represents the received channel CSI data and,
Figure DEST_PATH_IMAGE011
indicating the CSI data that is not shifted,
Figure DEST_PATH_IMAGE012
is (a)
Figure 657661DEST_PATH_IMAGE007
) The resulting offset;
the high-precision clock ensures that the chip sends a return signal while receiving the signal;
the WiFi positioning module at the mobile point end modulates a return frame by the MIMO and OFDM methods, and transmits the return frame through the antenna array, and at the moment, the phase shift is generated due to the phase-locked loop at the mobile point end
Figure 234136DEST_PATH_IMAGE006
；
The modulated return frame is transmitted in the space, and tiny frequency deviation is generated in the process of transmitting the mobile point terminal antenna
Figure 675350DEST_PATH_IMAGE003
The base station antenna generates tiny frequency deviation in the receiving process
Figure 552040DEST_PATH_IMAGE002
；
The modulated return frame is captured by the base station A and processed by the base station chip to obtain
Figure DEST_PATH_IMAGE013
PLL frequency offset generated at this time
Figure 718710DEST_PATH_IMAGE001
；
In the above-mentioned transmission process, the mobile station will receive
Figure 782481DEST_PATH_IMAGE005
Transmitting to a base station, the mobile point terminal will receive
Figure 284176DEST_PATH_IMAGE005
The transmission mode to the base station comprises: when sending the return frame, will
Figure 749793DEST_PATH_IMAGE005
As data, sent together; or after sending the return frame, will alone
Figure 290627DEST_PATH_IMAGE005
As data to the base station; or the mobile point end will
Figure 107273DEST_PATH_IMAGE005
Sending the data to a server as data, and sending the data to a base station by the server;
using a CSI channel model representation, then
Figure DEST_PATH_IMAGE014
；
CFO elimination algorithm, principle is through
Figure 687028DEST_PATH_IMAGE005
And
Figure 7151DEST_PATH_IMAGE013
the calculation of (2) eliminates the error generated in the middle;
according to the CSI channel model, there are
Figure DEST_PATH_IMAGE015
The CFO phase offset can be eliminated.
3. The system according to claim 1 or 2, wherein the phase extraction and subcarrier phase error elimination module is configured to estimate the phase of subcarrier 0 in the OFDM propagation model to obtain the final phase value.
4. The system of claim 1, wherein the ToF distance estimation is performed by obtaining ToF values of different frequencies by using a frequency hopping sampling technique, and solving by using the chinese remainder theorem to obtain a unique ToF value.
5. The system according to claim 3, wherein the estimating of the phase of the sub-carrier 0 in the OFDM propagation model to obtain the final phase value specifically comprises:
the base station WiFi model processes the CSI signals after CFO elimination, 30 subcarrier phase values of OFDM are extracted, and in the wireless signal propagation model of OFDM, the phase value of each subcarrier
Figure DEST_PATH_IMAGE016
Presence of frequency offset
Figure DEST_PATH_IMAGE017
，
Figure DEST_PATH_IMAGE018
For the frequency at which the carrier wave is transmitted,
Figure DEST_PATH_IMAGE019
for time of flight, the relationship is as follows:
Figure DEST_PATH_IMAGE020
since the sub-carrier No. 0 has no frequency offset and the OFDM sub-carriers are numbered-15, -14, … -1,1, …,14,15, the phase values of the sub-carrier No. 0 are estimated using the phase values of-1 and 1.
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